Inflatable safety restraint devices, or airbags, are mandatory on most new vehicles. Airbags are typically installed as part of a system with an airbag module in the steering wheel on the driver's side of car and in the dashboard on the passenger side of a car. In the event of an accident, a sensor within the vehicle measures abnormal deceleration and triggers the ignition of a charge contained within an inflator. Expanding gases from the charge travel through conduits and fill the airbags, which immediately inflate in front of the driver and passenger to protect them from harmful impact with the interior of the car. Typically, airbags are concealed within the vehicle trim to be invisible during normal vehicle operation.
Airbag systems have also been developed in response to the need for similar protection from lateral impacts between a passenger and the side of a vehicle's interior. This might occur when another vehicle collides with the side of the vehicle, or in a rollover situation where the side of the vehicle is repeatedly impacting the ground. Side impact airbags are often called “inflatable curtains.” Many inflatable curtains are stowed along the corner where the vehicle roof meets the side windows and pillars. These inflatable curtains may be stowed behind the headliner trim at the edge of the headliner, which is the fabric covering the roof of the vehicle.
Recent safety standards issued by various governments require more comprehensive protection in the event of a side or frontal collision. Additionally, there is an ongoing need to provide airbag systems that are more economical to manufacture and install, avoid interference with the ability of the automaker to position various features on the vehicle interior, and can be expected to deploy reliably. The passengers of a vehicle may be at any of a wide variety of positions within the vehicle at the time of deployment, so it is desirable to provide airbag systems that protect against impact over the broadest possible range of occupant locations.
It has been observed that some existing inflatable curtain designs do not provide adequate protection in the event of certain collision events, such as rollover collisions. In a rollover collision, the position and trajectory of vehicle occupants is difficult to predict. Accordingly, known inflatable curtains designed to protect against a pure lateral impact may not be in the proper position to provide the protection that is most needed. The result may be injuries from impact with interior vehicle surfaces and/or ejection from the vehicle, despite deployment of the airbag systems.
Additionally, it is desirable to reduce the cost, complexity, and manufacturing time of airbags. Many airbags are made from layers of material that are secured together to define the inflatable chambers of the airbag. Many known airbag designs have a substantial non-inflatable peripheral region that consists essentially of wasted fabric. The wasted fabric adds to the cost of the airbag because excessive fabric must be purchased and processed.
Furthermore, a wide variety of airbag system components may be used. Such components include a wide variety of tethers that help to control the deployment and/or positioning of the airbag. Such components are often formed separately from the airbag and attached to the airbag through the use of additional manufacturing steps. Thus, these accessories often add significantly to the cost and manufacturing time required to make the airbag.